The invention has to do with graphic arts of the kind which conventionally employ halftone reproduction methods, generally of the photoengraving type, usually heretofore utilizing physical "screens" in combination with suitable camera equipment, special optical stops, diaphragms and the like, to break up continuous tone original subject matter, photographs or other art work and provide photographic reproductions having a dot structure from which printing plates, for color or monochrome, can be fashioned. A considerable degree of camera work artistry is required of the operator as well as a great deal of opto-mechanical expertise and processing labor, in order to produce half-tone negatives (or positives) which retain the sharpness, information content, and other desired properties of the original subject matter.
It has already been proposed to generate halftones by "electronic" means, the approaches being generally similar to those described in the following publications:
"Electronically Generated Halftones," R. J. Klensch et al., RCA Review, September, 1970, pp. 517-533. PA1 "Electronic Halftones," R. Hallows et al., IEEE Spectrum, October, 1968, pp. 64-72. PA1 U.s. pat. No. 3,646,262, issued Feb. 29, 1972. However, these and similar prior proposals have not proved to be wholly satisfactory as to quality, cost and convenience.